#!/bin/bash

for image in *.{gif,bmp,jpg,wmf,jpeg,png}
do
    size=`/usr/bin/identify $image`
    ...
    [do whatever with "$size" here]
    ...
    convert -geometry 800x600 $image ${image/./-l.}
    convert -geometry 80x60 $image ${image/./-s.}
done

##</code><code>##

ben@Tyr:/tmp/Sorayama$ ../thumbnail
hajime1.jpg
hajime10.jpg
hajime2.jpg
hajime3.jpg
hajime4.jpg
hajime5.jpg
hajime6.jpg
hajime7.jpg
hajime8.jpgconverting hajime1.jpg ...
convert: invalid argument for option `hajime1-l.jpgxhajime1.jpg!': -resize.
convert: invalid argument for option `hajime1-s.jpgxhajime1.jpg!': -resize.
converting hajime10.jpg ...
converting hajime2.jpg ...
convert: invalid argument for option `hajime2-l.jpgxhajime2.jpg!': -resize.
convert: invalid argument for option `hajime2-s.jpgxhajime2.jpg!': -resize.
converting hajime3.jpg ...
convert: invalid argument for option `hajime3-l.jpgxhajime3.jpg!': -resize.
convert: invalid argument for option `hajime3-s.jpgxhajime3.jpg!': -resize.
converting hajime4.jpg ...
convert: invalid argument for option `hajime4-l.jpgxhajime4.jpg!': -resize.
convert: invalid argument for option `hajime4-s.jpgxhajime4.jpg!': -resize.
converting hajime5.jpg ...
convert: invalid argument for option `hajime5-l.jpgxhajime5.jpg!': -resize.
convert: invalid argument for option `hajime5-s.jpgxhajime5.jpg!': -resize.
converting hajime6.jpg ...
convert: invalid argument for option `hajime6-l.jpgxhajime6.jpg!': -resize.
convert: invalid argument for option `hajime6-s.jpgxhajime6.jpg!': -resize.
converting hajime7.jpg ...
converting hajime8.jpg ...
convert: invalid argument for option `hajime8-l.jpgxhajime8.jpg!': -resize.
convert: invalid argument for option `hajime8-s.jpgxhajime8.jpg!': -resize.